1. Field of the Invention
The present invention relates to improvements in an automatic seat-belt applying system for motorcars.
2. Description of the Related Art
In motorcars, there have been used seat belts for protecting driver and passengers on road accident. Recently, a passive seat-belt system has been proposed which automatically applies seat belts (shoulder belts) on a crew when they sit on seats.
FIG. 8 shows one of the conventional passive seat-belt systems, which is mounted on the driver's seat. The system comprises a guide rail 14 extending from a front pillar 10 through a roof side panel 11 to a center pillar 12, as shown in FIG. 8A. The guide rail 14 receives one end of a seat belt 16 (shown as a shoulder belt) through a movable member. The other end of the seat belt 16 is mounted in a retractor 20 under a predetermined tension, the retractor 20 being disposed adjacent to the left side of a driver's seat 18 (or the right side of a driver's seat if a steering wheel is disposed the left side of a motorcar).
As shown in FIG. 8B, the movable member of the seat belt 16 comprises an anchor 21 and a driving tape 22. The driving tape 22 is drivingly connected to a belt motor 24 which is disposed on the lower portion of the center pillar 12. The driving tape 22 is guided by a tape guide 25 between the guide rail 14 and the belt motor 24. After the driving tape 22 has been moved, the remaining portion thereof is received within a tape casing 26.
The automatic seat-belt applying system is automatically adapted to actuate the belt motor 24 through any suitable switch means when a driver sits on his seat 18 and if a door 27 is closed. On actuation of the belt motor 24, a sprocket 24a on the output shaft of the belt motor 24 is rotated to draw the driving tape 22, thereby tensioning the seat belt 16.
Thus, the one end of the seat belt 16 retracted in the front pillar 10 will be moved to a predetermined position in the center pillar 12 along the guide rail 14. During this movement, the seat belt 16 is applied to the driver while being drawn out from the retractor 20. When the one end of the seat belt 16 reaches said predetermined position in the center pillar 12, the anchor 21 is fixed to an anchor fixture (not shown) to complete the application of the seat belt.
If the driver wants to get out of the motorcar, he may actuate any suitable switch means to rotate the sprocket 24a in the opposite direction so that the driving tape 22 will be moved in the opposite direction to return the one end of the seat belt 16 to its original position in the front pillar 10. In this connection, the driving tape 22 can be replaced by any other suitable means such as wire or the like.
The other techniques for automatically applying the seat belt on the crew are disclosed, for example, in Japanese Utility Model Publication Nos. Sho 58-14130 and Sho 63-13082.
All these known techniques have the following disadvantages:
(1) The conventional automatic seat-belt applying systems are customary to perform the movement of the seat belt 16 by utilizing the driving tape 22 or wire so as to slidably move the one end of the seat belt 16 on the guide rail 14. This creates much loss of friction on moving the seat belt 16, resulting in increase of the capacity of the belt motor 24. There is required to secure an additional space which receives the driving tape 22.
(2) Since the seat belt 16 used is a shoulder belt, it is preferred that the anchor 21 (FIG. 8B) holding the one end of the seat belt 16 can be adjusted in height for the driver's sitting height. Although such an adjustment of the anchor's height has been proposed as by Japanese Patent Laid-Open Nos. Hei 1-101252 and Hei 1-223048, they are adapted to adjust the height of the anchor manually stepwise, for example, through three steps. This renders the adjusting operation complicated and also enables only rough adjustment to be performed. In such a case, it may be considered that in addition to the belt motor 24, an anchor driving motor for automatically moving the anchor is provided. As seen from FIG. 8, however, the provision of the driving tape 22 eliminates the possibility of any space for receiving such an anchor driving motor. Moreover, it is difficult in mechanism to provide the two different motors and associated transmission means in the limited space.
(3) In the prior art, furthermore, the seat belt 16 is wound by a retractor 20 under the action of a spring. Thus, the wound seat belt 16 is placed under a predetermined tension by means of the spring in the retractor 20. When the seat belt is applied to the driver, therefore, an oppressive sensation will be exerted about the body of the driver wound by the seat belt. Furthermore, the capacity of the belt motor 24 must be increased to draw the seat belt 16 against the tension applied thereto.